Children whose mothers return to full-time work before they are 18 months old are slower to develop basic learning skills, says a study published today.

The report said 14 per cent of mothers go back to full-time work in this time. It also found there were `significant ill-effects' on the development of children who were cared for by a friend, relative or neighbour full-time.

A Bristol University team said policies which encourage flexible and part-time working practices, or enable mothers to remain at home for longer after a birth could minimise the negative effects, as could paternity leave.